meld

Meld is a graphical diff viewer and merge application for the GNOME desktop. It supports 2 and 3-file diffs, recursive directory diffs, diffing of directories under version control (Bazaar, Codeville, CVS, Darcs, Fossil SCM, Git, Mercurial, Monotone, Subversion), as well as the ability to manually and automatically merge file differences.

Meld is bad for complex file comparison as you can't see inside the files. But you can delete or copy any file from any folder as you like. Kdiff3 is great for serious file comparisons as it has built in text viewers, I prefer Kdiff3's layout and method of merging into one folder but it won't let me delete files from one folder and not everything so here I am using Meld again as I want 3 separate folders without the same files, and Meld can do this.

Love this very light weight editor. It uses very little resource compare to kate. I use it with KSVN which allows my to compare the local files with the remote svn files, just right click on the file and choose 'diff' its that easy (must have KSVN installed).